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hashcash.go
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hashcash.go
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package provingwork
import (
"bytes"
"fmt"
"math/big"
"crypto/sha1"
"encoding/base64"
"encoding/binary"
"encoding/json"
)
// HashCash format:
// 1:20:20160927155710:somedatatovalidate::aW5ZdXJQcm90b2NvbHMh:VvJC
// version, zero bits, date, resource, extension (ignored), rand, counter
type HashCash struct {
Counter int64 `json:"counter"`
Resource []byte `json:"resource"`
*WorkOptions
}
// An alias type that won't have any of functions (mostly to avoid an infinite
// loop with the overidden MarshalJSON function)
type RawHashCash HashCash
// This is a special version of the HashCash that has the types we want to
// be importing / exporting.
type HashCashExt struct {
Timestamp int64 `json:"timestamp"`
*RawHashCash
}
func (wo HashCash) MarshalJSON() ([]byte, error) {
woe := HashCashExt{RawHashCash: (*RawHashCash)(&wo)}
if wo.Timestamp != nil {
woe.Timestamp = wo.Timestamp.Unix()
}
return json.Marshal(woe)
}
func (wo HashCash) UnmarshalJSON(data []byte) error {
woe := HashCashExt{RawHashCash: (*RawHashCash)(&wo)}
if err := json.Unmarshal(data, woe); err != nil {
return err
}
return nil
}
func NewHashCash(resource []byte, opts ...*WorkOptions) *HashCash {
hc := HashCash{ Resource: resource }
if len(opts) != 0 {
hc.WorkOptions = opts[0]
} else {
hc.WorkOptions = &WorkOptions{}
}
setDefaultWorkOptions(hc.WorkOptions)
return &hc
}
func (hc HashCash) Check() bool {
if hc.ZeroCount() >= hc.BitStrength {
return true
}
return false
}
func (hc HashCash) CounterBytes() []byte {
var buf bytes.Buffer
binary.Write(&buf, binary.BigEndian, hc.Counter)
return buf.Bytes()
}
func (hc *HashCash) FindProof() {
for {
if hc.Check() {
return
}
hc.Counter++
}
}
func (hc HashCash) String() string {
return fmt.Sprintf(
"1:%v:%v:%v:%v:%v:%v",
hc.BitStrength,
hc.Timestamp.Format("20060102150405"),
string(hc.Resource),
string(hc.Extension),
base64.StdEncoding.EncodeToString(hc.Salt),
base64.StdEncoding.EncodeToString(hc.CounterBytes()),
)
}
func (hc HashCash) ZeroCount() int {
digest := sha1.Sum([]byte(hc.String()))
digestHex := new(big.Int).SetBytes(digest[:])
return ((sha1.Size * 8) - digestHex.BitLen())
}